1. Field of the invention
The present invention concerns a drilling feeler, intended in particular for positioning a medullary nail, i.e. in bone surgery for axially securing a nail having an annular cross-section by means of pins simultaneously passing through the bone and the nail in a transversal direction.
2. Summary of the prior art
Are already known, especially from earlier French patent applications filed in the name of the applicant, 85.12777 dated August 25, 1985 and 86.11270 dated Aug. 13, 1986, feelers of this type in which a drilling head, mounted on the end of a spindle at least partially flexible and driven in rotation through the intermediary of coupling means, by a rotary motor, is guided within a guiding and positioning head introduced into the medullary nail. This guiding head is displaced in the said nail until the drilling head is placed opposite an inlet hole provided in the annular wall of this nail. Means are provided for blocking in rotation and in axial position the guiding head in this nail, so that the drilling head is correctly positioned during drilling and maintains its position.
However, in the feelers proposed up to now, these blocking means are produced, on the one hand, for the rotation, by the form of the cross-section of the guiding head, complementary with the cross-section of the nail, on the other hand, for the axial position, by ratcheting of a ball carried by this head, and engaged in an appropriately disposed bore on the wall of the nail, do not ensure a completely satisfactory locking of the axis of the drilling head; this results in particular from the operating clearance required between the guiding head and the internal wall of the nail and also due to the fact that the ratcheting ball is placed at a distance from the drilling head. Furthermore, experience has shown that the boring drill tends to slide on the bone surface and that it is necessary, to avoid any deviation of the drilling hole, to guide correctly the boring drill and to make it attack the surface of the bone along a line perpendicular to the surface.
The present invention aims at producing a drilling feeler that does not present these drawbacks.
The feeler according to the invention, intended to be associated to a medullary nail in which, through external gripping means, is introduced into the medullary nail and is placed in alignment with the axis of an inlet pin or screw hole of the wall of this nail, a drilling tool integral with a sliding block bearing means for positioning and blocking the said nail, this tool being mounted at the distal end of a driving rotating spindle, at least partially flexible, wherein the distal end of the spindle carrying the tool is housed in a bore of a sleeve protruding from a drilling head, said head being movable around an axle carried by the block sliding between a disengagement position allowing the sliding of the said head in the nail and an engagement position in which the sleeve is engaged in the inlet pin or screw hole, the feeler furthermore comprising a blocking wedge hinged to the end of a rod connected to the gripping means, this wedge being adapted to move closer to or away from the drilling head, in order to respectively maintain it in engagement position or allow its tilting towards disengagement position.
According to another characteristic, the drilling head comprises a nose-piece turned towards the blocking wedge, this nose-piece provided with a flattened portion, perpendicular to the axis of the sleeve and adapted to enter into contact with the internal wall of the nail in engagement position of the drilling head and a slope bearing surface adapted to cooperate, for this same engagement position, with a slope face of the wedge which is recalled towards the said drilling head through the intermediary of the rod cooperating with the gripping means.
According to another embodiment, the rod hingedly connected to the wedge and the driving spindle of the drilling head are housed in two parallel tubes, at the distal end of which is fixed the sliding block, the other end of these tubes being fixed to a body integral with the gripping means, these consisting of a clip comprising a fixed part integral with the said body and a movable part about a common axis and an extension of which is hinged to the proximal end of the rod, a spring urging the movable parts to spread apart from each other and thus to move closer together the wedges of the block. The distal end of the rod is connected to the blocking wedge through the intermediary of a slide movable in a slope ramp, provided in the wedge and having an axis substantially normal to the slope face, in such a manner that a return of the wedge towards the drilling head, in contact with the slope bearing surface of this head, pushes this wedge into contact with the internal wall of the nail by consolidating the locking of the assembly.
According to one advantageous disposition of the feeler, the sliding block and the wedge present at least partially complementary cross-sections of the cross-section of the associated medullary nail.